Valve mechanism

Abstract

A pneumatic valve mechanism, especially for controlling the movement of paper, comprises a mouthpiece (47) which defines an air intake (58), a bellows (10) coupled to the mouthpiece, a passage (42, 44) connecting the interior of the bellows to a pump so that when the bellows is not fully retracted suction is created at the air intake (58) and a seal (50) between the mouthpiece and a valve body (14) which is effective when the bellows is fully retracted, following closure of the air intake by a sheet of paper (60), to seal the air intake from the suction pump. Venting air can enter the mouthpiece in the retracted position of the bellows, to permit the sheet to drop off the intake, but without breaking the seal (50), whereby the bellows is maintained in its retracted position. The bellows (10) will only extend again to seek the next sheet when the effect created by the suction pump is interrupted, as by breaking the seal (50) by energizing a solenoid (64) and displacing a mechanical linkage (62,54).

I claim: 
     
       1. A pneumatic valve mechanism comprising a mouthpiece which defines an air intake; an extensible and retractable sleeve, normally biased at an extended position, coupled to the mouthpiece to cause the mouthpiece to move therewith; passage means to connect the interior of the sleeves to suction means such that when the sleeve is not fully retracted suction is created at the air intake; wherein, when the air intake is closed, the sleeve is retracted by the effect of the suction; a seal between the mouthpiece and a valve body within the sleeve which is effective when the sleeve is fully retracted, following closure of the air intake, to seal the air intake from the suction means; venting means permitting air to enter the mouthpiece in the retracted position of the sleeve without breaking the seal, whereby the sleeve is maintained in its retracted position by the effect of said suction; and actuating means arranged upon operation to break the seal and thereby permit the biased sleeve to return towards its extended position. 
     
     
       2. A valve mechanism as claimed in claim 1, in which the extensible and retractable sleeve is a bellows. 
     
     
       3. A valve mechanism as claimed in claim 1 or 2, in which the mouthpiece comprises a suction cup. 
     
     
       4. A valve mechanism as claimed in claim 3, in which the suction cup itself defines a sealing surface engageable with the valve body to form the seal. 
     
     
       5. A valve mechanism as claimed in claim 3, in which the mouthpiece comprises a generally tubular member having the suction cup at one end thereof and sealing means at the other end thereof. 
     
     
       6. A valve mechanism as claimed in claim 5, in which a guide rod extends from the valve body through and out of the mouthpiece, the venting means comprising an aperture in the mouthpiece around the guide rod. 
     
     
       7. A valve mechanism as claimed in claim 5, in which the mouthpiece includes a guide rod movable with the tubular member and extending longitudinally through the bore thereof, the guide rod being received at its other end in a guide tube rigidly connected to the valve body, the venting means comprising a passageway between the guide rod and the guide tube. 
     
     
       8. A valve mechanism as recited in claim 1, in which the mouthpiece comprises a boot which defines the ar intake and which is shaped to collapse eccentrically when it comes into contact with and grips a sheet of material, thereby initiating a peeling movement of the sheet. 
     
     
       9. A valve mechanism as recited in claim 1, in which said actuating means comprises switching means arranged to interrupt the effect of the section means. 
     
     
       10. A valve mechanism as recited in claim 1, in which said actuating means comprises electromagnetic means arranged to control movement of a mechanical linkage, displacement of which causes the seal to be broken.